GPA and MPA are two autoimmune disorders that cause systemic vasculitis. GPA commonly affects the upper respiratory tract, the lungs, and the kidneys. MPA is marked by kidney inflammation, weight loss, skin lesions, nerve damage, and fever. Many patients with WG or MPA show no visible symptoms of active disease; it is known that underlying subclinical disease activity leads to long-term damage in these patients. Also, because it is difficult to monitor WG and MPA disease activity, it is difficult for clinicians to know when and how to treat these patients. This study will use new scientific methods to identify new biomarkers that can be used to monitor disease activity in GPA and MPA patients. These biomarkers may be used to help direct clinical care for GPA and MPA patients and assist in future drug development.